The objectives of this project are to determine the molecular mechanisms of action of the neurotransmitter gamma-aminobutyric acid, in mammalian brain homogenates, including human. Using radioactive ligand binding for the GABA receptor protein and radioactive picrotoxin and benzodiazepines to assay membrane sites related to GABA receptor function, we are studying the biochemical and functional properties of these post-synaptic GABA receptor-ionophore (drug-binding) proteins in human and other mammalian brain membranes, in crayfish muscle.